The fruits and vegetables we buy in the grocery store are actually still alive and according to new research from Rice University and the University of California at Davis, produce may be healthier for us depending on the time of day.

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"Vegetables and fruits don't die the moment they are harvested," said Rice biologist Janet Braam, lead researcher of the study.

Once picked, produce can continue to metabolize and survive independently for some time. Even when they are cut, their cells remain active and alive.

"They respond to their environment for days, and we found we could use light to coax them to make more cancer-fighting antioxidants at certain times of day," says Braam who is also a professor and chair of Rice's Department of Biochemistry and Cell Biology.

Braam's team shows that post-harvest vegetables and fruits can continue to perceive light and, as a result, their biological clocks keep on ticking. This is an advantage to the plants because it allows them to alter levels of important chemicals that protect them from being eaten by insects and other herbivores, the researchers found. This includes the process of ripening as these fruits and vegetables will often wait to ripen until their seeds are mature enough to germinate.

The research also shows that when it comes to human consumption, post-harvest fruits and vegetables may contain higher levels of phytochemicals at different times, which have have anti-cancer effects.

Braam's team simulated day-night cycles of light and dark to control the internal clocks of fruits and vegetables, including cabbage, carrots, squash and blueberries.

"Vegetables and fruits, even after harvest, can respond to light signals and consequently change their biology in ways that may affect health value and insect resistance," says Braam. "Perhaps we should be storing our vegetables and fruits under light-dark cycles and timing when to cook and eat them to enhance their health value."

While the science indicates we may want to consider our foods' daily schedules when deciding what time to eat them, this may not be convenient to the average family. However, "It may be of interest to harvest crops and freeze or otherwise preserve them at specific times of day, when nutrients and valuable phytochemicals are at their peak," Braam says.